Industrial Ventilation & Ducting
The importance of clean uncontaminated air in the industrial work environment is well known. Modern industry with its complexity of operations and processes uses an increasing number of chemical compounds and substances, many of which are highly toxic. The use of such materials may result in particulates, gasses, vapours, and /or mists in the workroom air in concentrations which exceed safe levels. Effective, well designed ventilation systems offer a solution to these problems where worker protection is needed. Ventilation can also serve to control odour, moisture, and other undesirable environmental conditions.
Ventilation systems used in industrial plants are of two generic types. The SUPPLY systems used to supply air, usually tempered, to a work space. The EXHAUST system is used to remove the contaminants generated by operations in order to maintain a healthy and corrosive free work environment.
A complete ventilation program must consider both supply and exhaust systems. If the overall quantity of air exhausted from a work space is greater than the quantity of air supplied tp the work space, the plant interior will experience a lower pressure than local atmospheric pressure. This will lead to the air entering the plant in an uncontrolled fashion i.e. through doorways, cracks, walls ceiling and windows. This typically results in worker discomfort and other
Exhaust ventilation systems are classified in two generic groups 1) the GENERAL exhaust system and 2) the LOCAL exhaust system.
The GENERAL exhaust system can be used for heat control and removal of contaminants generated in a space by flushing out a given space with large quantities of air. These systems usually are large, cumbersome and expensive to install and run.
The local ventilation system operates on the principle of capturing a contaminant at or near to the source of generation. It is the preferred method of control because it is more effective and uses smaller exhaust flow rates. Local exhaust systems are comprised of four basic elements-
- Canopy type hoods, Fume cupboards, Lateral exhaust hoods, and Spray booths.
- Ducting system including exhaust stack and/or recirculation ducting.
- Air cleaning device such as Scrubbers (chemical and biological), Reverse Pulse Dust filters and Activated Carbon filters.
- Exhaust Fans.
The purpose of the hood is to exert control and collect the contaminated air . A duct system will transport the contaminated air to the air cleaning device, if present and the fan. In the air cleaning device the contaminant is removed from the air stream. The fan will overcome all losses due to friction, hood entry, and fittings in the system while producing the intended flow rate.